1. Technical Field
The present invention relates to a magnetic recording medium used for a hard disc, magnetic tape, floppy disc, magneto-optical disc, and the like.
2. Prior Art
While there is an increasing demand for high-density recording of information, the in-plane magnetic recording for regarding magnetic recording media causes a problem of thermal demagnetization in which recording magnetization attenuates with the lapse of time.
The vertical magnetic recording is a technique of solving the problem of the in-plane magnetic recording. A CoCr alloy is widely researched as a magnetic material for vertical magnetic recording media.
When the CoCr alloy is used as a magnetic material for vertical magnetic recording media, its vertical magnetic anisotropy is smaller than the saturation magnetization. This causes a disadvantage that a vertical rectangular ratio does not become 1. Consequently, a reverse magnetization region is generated in a long wavelength recording portion on a CoCr alloy""s magnetic layer. It is widely known that this causes a noise.
This problem can be solved by using a material with increased vertical magnetic anisotropy for the magnetic layer of vertical magnetic recording media. An example of such a magnetic layer is a layered magnetic layer which is formed by alternately layering Co and Pt or Pd.
When the magnetic recording medium includes such a layered magnetic recording layer formed by alternately layering Co and Pt or Pd, a vertical magnetic anisotropy magnetic field on the layered magnetic recording layer is sufficiently larger than demagnetization due to saturation magnetization. The layered magnetic layer causes little noises, but too much transition noises, which are ineffective for short wavelength recording.
The present invention has been made in consideration of the foregoing. It is therefore an object of the present invention to provide a magnetic recording medium having a layered magnetic recording layer formed by alternately layering Co and Pt or Pd characterized by greatly decreasing transition noises in the layered magnetic recording layer and suited for short wavelength recording with an excellent S/N ratio.
A magnetic recording medium according to the present invention comprises an artificial lattice film formed by alternately layering a Pt or Pd layer and a Co layer and is characterized by having a vertical magnetic recording film containing B and O.
A magnetic recording medium according to the present invention comprises an artificial lattice film formed by alternately layering a Pt or Pd layer and a Co layer as a layered magnetic recording layer and includes a vertical magnetic recording film containing B and O. Because of this, the transition noises are greatly decreased in the layered magnetic recording layer.
As mentioned above, a magnetic recording medium according to the present invention comprises an artificial lattice film formed by alternately layering a Pt or Pd layer and a Co layer as a layered magnetic recording layer and includes a vertical magnetic recording film containing B and O. Because of this, the greatly decreases transition noises in the layered magnetic recording layer.
Accordingly, the present invention can provide a magnetic recording medium characterized by greatly decreasing transition noises in a layered magnetic recording layer and suited for short wavelength recording with an excellent S/N ratio.